This invention relates to the production of 5-aroyl-pyrrole compounds. Such compounds are known and described in U.S. Pat. No. 3,752,826 to Carson. According to the teaching of Carson, compounds such as 5-aroyl-pyrrole alkanoic acids and the corresponding salts, esters, nitriles, amides and substituted amides are prepared by Friedel-Crafts reaction between an appropriate aroyl halide (I), preferably chloride, and a pyrrole-2-acetic acid derivative (II), such as the cyano or lower alkoxy-carbonyl, in the presence of a Lewis acid, preferably a metallic halide, such as aluminum chloride to form 5-aroyl-pyrrole-2-acetic acid derivatives (III). The reaction of Carson is shown in the following schematic diagram: ##STR1## in which Ar represents a member selected from the group consisting of phenyl, thienyl, 5-methylthienyl mono-substituted phenyl and poly-substituted phenyl, each substituent of said substituted phenyls being a member selected from the group consisting of halo, lower alkyl, trifluoromethyl, lower alkoxy, nitro, amino, cyano and methylthio; R represents a member selected from the group consisting of hydrogen and lower alkyl; R.sub.1 represents a member selected from the group consisting of hydrogen, lower alkyl and benzyl, and R' is cyano or lower alkoxy-carbonyl. Suitable solvents are those typically employed in Friedel-Crafts reaction such as methylene chloride, 1,2-dichloroethane, carbon disulfide, nitrobenzene and the like. The 5-aroyl-pyrrole-2-acetic acid derivative (III) can then be converted to corresponding 2-carboxylic acid by conventional hydrolysis. For example, by heating a solution of the 5-aroyl-pyrrole-2-acetic acid derivative with an alkali metal hydroxide to form the alkali metal salt of the acid and then acidifying the mixture.
A wide variety of 5-aroyl-pyrroles are produced according to the process schemes shown in Carson. Such compounds have useful pharmacological properties which make them suitable for formulation in conventional pharmaceutical forms for administration. The 5-aroyl-pyrrole compounds described in Carson have been found to possess anti-inflammatory activity which has been demonstrated in standard kaolin-induced rat paw edema and cotton pellet granuloma tests at doses generally ranging from 5-100 mg/kg body weight. Accordingly, improved processes for acylating the pyrrole-2-acetic acid derivatives are desirable. Thus, it is an object of the present invention to provide a process for preparing 5-aroyl-pyrrole-2-acetic acid derivatives, and particularly 5-aroyl-pyrrole-2-acetonitrile, in higher yields, using a process providing advantages over the prior art. The foregoing and other objects are accomplished by the process of the present invention.